The (New) Stanford Light Field Archive

Computer Graphics Laboratory, Stanford University

Listed below are the light fields in our archive. For each light field, there
is a link to the imagery - sometimes in several forms, and sometimes
accompanied by calibration information. Following this is a link that allows
you to view the light field in your browser using our Flash-based light field
viewer.

Notes about the light field viewer

In most cases you shouldn't need to download any software to use our viewer;
just click on the indicated links below. Be warned though, this involves
loading the entire light field (usually at slightly reduced spatial resolution)
into memory. For the largest light fields, this involves downloading about
30MB of data, and will cause your browser to use up to a gigabyte of RAM.
Firefox 3 uses notably less RAM than Firefox 2 when viewing these light fields,
as does Internet Explorer 7. Safari and Opera should also work, with the
appropriate flash player plugin.

You're free to take the viewer and use it for your own light fields. The source code and instructions for the using or modifying viewer are available.

Instructions for the viewer

Once the light field loads, click and drag in the dark gray area on the left to change the point of view.

Shift click in the dark gray area to change the size of the synthetic aperture.

You can also click the 'Full Aperture' and 'Pinhole Aperture' buttons to change the size of the aperture.

Click the slider way over on the right to manually focus through the scene. It's best to do this with a medium-sized aperture.
Make sure your browser window is wide enough to see this slider.

For some scenes, you can click on the image itself to autofocus at that point.

These instructions are all available within the viewer itself, if you click the 'How do I use this?' button.

The online viewer was written by Andrew Adams. The idea for the autofocus interaction was taken from Ren Ng's cool demos at Refocus Imaging.

A lego scene. Contains relatively simple geometric
objects at various depths. The lego is slightly
specular, and untextured in many places, making
depth reconstruction more challenging than you would
expect for this scene. The regular grid of studs on
the base plate provides a good demonstration of
synthetic focus.

A scene with a crystal ball resting on tarot
cards. The ball acts as a lens. The cards act as
diffuse textured objects at many orientations and
depths. This light field is captured at larger
angular extent than the next one, and hence contains
more angular aliasing - this is good for depth
reconstruction but bad for refocusing.

The same scene as above, captured with smaller
camera spacing. This has less angular aliasing, and
is hence better for refocusing and worse for depth
reconstruction. The camera is at F/8 at 22mm, so the
size of the aperture was 2.75mm. The spacing between two camera
positions was just under half of this (roughly 1.33mm).

The lego gantry capturing itself, looking in a
mirror. The gantry naturally moves as it captures
itself, which results in some unusual apparent
depths for each object. Furthermore, the gray towers
move vertically but not horizontally, giving them
one apparent depth from horizontal parallax, and a
different depth from vertical parallax. The focus is
hence astigmatic. More usefully, panning the scene
shows all the positions the lego gantry moves through.

Microscope Light Fields

The light fields in this section were acquired by
Marc Levoy.
More detail on these datasets can be found at the Light Field
Microscope page. Some things to be aware of when viewing these light
fields using the Flash-based viewer:

They are low resolution. Unlike the other light fields on this
page, these were captured with a single snapshot from a single camera. This
means fewer total samples are available to record all the spatial and angular
information, so the ouput spatial resolution is low. Even if we had multiple
cameras, diffraction places a fundamental physical limit on the product of
spatial and angular resolution we could capture. If you're more comfortable
thinking of light as particles than as waves, then one way to think of this is
as an application of the Heisenberg uncertainty principle. You can either know
where a photon is (high spatial resolution), or know its momentum (high angular
resolution, i.e. views from lots of directions), but you can't know both with
high accuracy.

The output looks pixelated. This occurs because the original light
fields have low spatial resolution, so the output window is upsampled for
easier viewing. To view the light field at the original small resolution, use
the 'with no magnification' links. You can also change the magnification by
tweaking the zoom parameter in the url.

The output becomes darker when using the full aperture. This occurs
because brightness falls off as you approach the edges of the aperture in a
microscope, hence these samples are dim. You can see this by using a pinhole
aperture and panning slowly to the edge of the view for each light field, or
slowly shrinking the aperture from full to pinhole. Our LFDisplay
viewer (see below) normalizes the rendered image automatically to avoid this
darkening.

A sudden jump happens at the very edges of the aperture. This
occurs when adjacent lenslet images slightly overlap in the rectified camera
image, which means views from opposite sides of the microscope aperture add
together on the sensor. Tweaking the numerical aperture (NA) of the microscope
objective or the F-number of the microlenses would have eliminated this
crosstalk.

You can also view these light fields using
LFDisplay,
our hardware-accelerated viewer for microscope light fields. This viewer
requires downloading an executable, but it won't have the resolution
limitations of the Flash-based viewer.

The specimen is a 200-micron-tall "tower" of
fluorescent crayon wax. The objective is 20x/0.5
(dry), used without a cover slip. The parallax you
see in this light field is normally unavailable to the
microscopist, who only sees a single, orthographic view
of the specimen.

A Golgi-stained slice of rat brain (courtesy of Shinya Inoue,
Marine Biological Laboratory), imaged with a 20x/0.75NA (dry)
objective. Lateral spatial resolution on the specimen is 1.5
microns. Angular resolution is about 5 degrees. In other
words, when panning across the light field in pinhole mode
using our Flash-based viewer, each step is 5 degrees.

The same slice of rat brain as above, imaged with a 40x/1.3NA
oil immersion objective. Note the large amount of parallax
in this light field. A 1.3NA objective can capture rays
leaving the specimen at angles up to 59 degrees on either
side of the optical axis. For photographers, this would
correspond to a lens having a relative aperture of f/0.58 -
far faster than any commercially available photographic lens.

This light field is identical to the previous one except that dense foliage was placed in front
of the humvee and soldier. The exposure time was also increased and lights turned up slightly
to avoid dark regions.